Specialized catheter and method for placement in a bifurcated vessel

ABSTRACT

A specialized catheter is used in a method to place a stent assembly in a bifurcated vessel in an animal body, such as a human. Primary and secondary guidewires are inserted from a location external of the body through the primary vessel, the secondary guidewire being further inserted into a secondary vessel beyond a bifurcation area. The guidewires are inserted into a primary stent and catheter assembly such that the assembly can move along the guidewires to the bifurcation area where the primary stent is expanded. While retaining the secondary guidewire in the vessels, the primary catheter assembly and primary guidewire are removed, the secondary guidewire passing through specialized openings in the primary catheter. Then the secondary stent, mounted on a catheter, is passed through the primary vessel guided by the secondary guidewire, and into the secondary vessel. There, the secondary stent is expanded to form the bifurcated stent assembly in an efficient manner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/428,934, filed Jul. 6, 2006, now U.S. Pat. No. 7,824,438,issued Nov. 2, 2010, the entire disclosure of which is herebyincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a specialized catheter and a method ofplacing the catheter and stents in a bifurcated vessel. Moreparticularly, the method includes placing a primary stent in a primaryvessel and a secondary stent in at least one secondary vessel whichbranches from the primary vessel, the secondary branch vessel(s) and theprimary vessel forming at least one bifurcated vessel. The catheter isspecialized to allow passage of a guidewire through the wall of thecatheter and remove the primary stent assembly so that the secondarystent may be placed into position in the secondary vessel.

A stent, sometimes referred to as a graft, is an endoprosthetic devicethat is placed within or implanted in a tubular vessel, such as avascular vessel like an artery or vein, or other vessel, such asintestine, esophagus or other tubular body organ in animals, andparticularly humans, for treating blockages, stenoses or aneurysms ofthe vessel. The stent is implanted within the vessels to act as aninternal scaffold or reinforcement to support collapsing, previouslyfully or partially occluded, weakened or abnormally dilated portions ofthe vessel wall. Typically, stents have been used to treat dissectionsin blood vessel walls, for example following balloon angioplasty of thecoronary arteries and peripheral arteries, and to improve results ofangioplasty by reinforcing the vessel wall. Stents also have beenimplanted in other body vessels, such as the gastrointestinal tract,particularly the urinary tract, the bile duct, the esophagus and thetracheo-bronchial tree to support weakened or otherwise damaged walls ofthose organs.

Typically, stents are elongated tubular products that have a first,unexpanded condition in which they are threaded through the appropriatebody organs, such as blood vessels, by use of catheters and guidewires.Some stents are expanded by way of the use of a small balloon which isexpandable by a fluid, such as a sterile saline solution, when the stentreaches the desired location. There are great number of examples ofstents having various types of geometry, such as those disclosed in U.S.Pat. No. 4,739,762 of Palmaz (commercialized in various forms as thePalmaz stent), U.S. Pat. No. 5,895,406 of Gray et al. and U.S. Pat. No.5,922,021 of Jang. Other types of stents have been developed that aremade of materials, such as an alloy of nickel and titanium callednitinol, which, when initially compressed, are within the sheath of acatheter, are in an unexpanded state, but when released from thecatheter sheath, self-expand to an appropriate degree without the use ofa balloon to bear against the vessel walls and retain them in an opencondition. A couple of examples of stents of this type are shown in U.S.Pat. No. 6,923,829 of Boyle et aL and U.S. Pat. No. 6,936,066 of Palmazet al. Stents have been commercialized by Cordis Corp. (a Johnson &Johnson Company), Guidant Corp., Boston Scientific Corp., MedtronicInc., all of the United States, and Medinol, Ltd. of Israel, amongothers. The manufacture and installation of stents is a multi-billiondollar business which is increasing annually, particularly aspopulations age.

Some stents are drug-eluting stents by virtue of the material from whichthe stents are made having properties particularly relating toantithrombotic activity, or antirestenosis activity. Often duringprocedures relating to vessel repair or even the insertion of thestents, blood may form clots, resulting in potentially serious or fatalthromboses and, over time, scar tissue or other matter builds up in thevessels, often in the vicinity of and on, and even as a result of, theuse of a stent, resulting in re-blockage or restenosis of the vessel.Drug-eluting stents, which may also include coatings, thin reservoirscontaining leachable active ingredients, and other techniques, have beendeveloped and are in use to help prevent or treat such thromboses orrestenosis. Among a great many examples are drug-eluting stents of atype disclosed in U.S. Pat. No. 6,120,536 of Ding et al., or U.S. Pat.No. 7,037,332 of Kutryk et al., which discloses a device coated with anantibiotic that promotes adherence of endothelial cells to the device.Certain materials used in making stents are themselves antirestentoticor antithrombogenic, such as U.S. Pat. No. 6,379,383 of Palmaz et al.

The use of stents in relatively straight and unbranched vessels isfairly straightforward. Complications arise when the damage to berepaired is near or at ajunction or point of bifurcation in bifurcatedvessels where a branch vessel joins a main vessel. There aredifficulties in inserting stents both in the main or primary vessel andin the branched or secondary vessel, which may result in further damageto the vessel with increased risk of thrombosis and embolism or evenadditional perforation of the vessel. Complications that may arise aredisclosed in U.S. Pat. No. 6,962,202 of Vardi et al., which disclosesone type of apparatus and a method of using it for treating bifurcatedvessels. Other examples of stents and methods of inserting them for usein bifurcated vessels are disclosed in U.S. Pat. No. 6,440,165 ofRichter et al. and in U.S. Patent Application Publication No. US2004/0186560, published Sep. 23, 2004. The disclosures of these and allother patents and publications mentioned herein are hereby incorporatedherein by reference. Each of the patents or publication mentioned inthis paragraph discloses alternative arrangements and methods ofinsertion. Despite the various techniques, there are still certaininefficiencies and concerns with the methods of inserting stentassemblies in bifurcated vessels. The present invention overcomes thedifficulties in alignment and insertion of various types of stents.

The present invention provides a specialized primary stent catheter andthe method of its use to positively and efficiently align and insert astent assembly comprising a primary stent and a secondary stent into abifurcated vessel. The stent may be a balloon-expandable stent or aself-expandable stent and may include a coating or be made of materialsby which it may also be a drug-eluting stent. The stent is made ofmaterials or includes imageable coatings or other markings to allowready determination of its location within and passage through a vessel,which is particularly important when dealing with bifurcated vessels.Such coatings and technologies are well known to those skilled in theart. Substantially any type or configuration of stent may be used withthe method of the present invention.

A portion of the primary catheter is separable so that after a primaryguidewire guides the primary stent into a primary vessel, a secondaryguidewire may be removed from the lumen of the primary catheter andguide a secondary stent into a secondary vessel. The separable portionof the catheter does not significantly protrude from a cross-section ofthe catheter, thus making the surface of the catheter less obtrusive asit travels through a vessel than would an external guide mounted on thebody of the catheter.

The present invention provides for an improved catheter to guide thestent assembly into a bifurcated vessel, along with the method forplacing the stent assembly into the bifurcated vessel, with completestent support for the full bifurcated vessel, which reduces the risk ofrestenosis or other adverse consequences associated with treatingbifurcated vessels.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention relates to a method for placing astent assembly in a bifurcated vessel in an animal body, the methodcomprising (a) locating and assessing an area in the body for placementof a stent assembly in a primary vessel and a secondary vessel at alocation where the primary vessel and the secondary vessel intersect ata bifurcation area; (b) inserting a primary guidewire from a locationexternal of the body through the primary vessel beyond the bifurcationarea; (c) inserting a secondary guidewire from a location external ofthe body through the primary vessel and into the secondary vessel; (d)selecting a primary stent having a lumen, a side opening, a proximal endregion and a distal end region, the primary stent being configured tofit within the primary vessel in the bifurcation area, and whenexpanded, to maintain patency of the primary vessel where the primarystent is installed; (e) mounting the primary stent on a primary stentcatheter having a lumen and a side opening such that the primary stentis expandable when in position in the bifurcation area and the sideopening of the primary stent is aligned with the side opening of theprimary stent catheter; (f) inserting the primary guidewire through thelumen of the primary stent catheter surrounded by the distal end portionof the primary stent and extending through the lumen of the primarystent catheter surrounded by the proximal end region of the primarystent; (g) inserting the secondary guidewire into the aligned sideopenings of the primary stent and the primary stent catheter andextending through the lumen of the primary stent catheter surrounded bythe proximal end region of the primary stent; (h) passing the primarystent catheter through the primary vessel and into the bifurcated areafor placement of the primary stent within the primary vessel; (i)expanding the primary stent to maintain patency of the primary vessel inand adjacent to the bifurcation area, such that the side opening in theprimary stent is aligned with the secondary vessel; (j) withdrawing theprimary stent catheter and, optionally, the primary guidewire from theprimary vessel, while retaining the secondary guidewire in the primaryand secondary vessels; (k) selecting a secondary stent having a lumen, aproximal end region and a distal end region, the secondary stent beingconfigured to fit within the secondary vessel in the bifurcation area,and when expanded, to maintain patency of the secondary vessel where thesecondary stent is installed; (l) mounting the secondary stent on asecondary stent catheter having a lumen such that the secondary stent isexpandable when in position through the side opening of the primarystent in the bifurcation area and when in position in the secondaryvessel; (m) inserting the secondary guidewire into the secondary stentcatheter lumen beginning from a portion surrounded by the distal endregion of the secondary stent and extending through the lumen of thesecondary stent catheter surrounded by the proximal end region of thesecondary stent; (n) passing the secondary stent catheter through theprimary vessel, through the proximal end region and side opening of theexpanded primary stent into the bifurcated area for placement of thesecondary stent within the secondary vessel and in fluid communicationwith the expanded primary stent; (o) expanding the secondary stent tomaintain patency of the secondary vessel such that the proximal endregion of the secondary stent is in fluid communication and in contactwith the side opening of the expanded primary stent; and (p) withdrawingthe secondary stent catheter and the secondary guidewire, and theprimary guidewire if the primary guidewire was not previously withdrawn,from the secondary and primary vessels to a location external of thebody.

Another aspect of the present invention relates to a catheter comprisinga tubular body, a lumen extending through the tubular body, a proximalend of the tubular body, a distal end region terminating at a distal endof the tubular body opposite the proximal end, the tubular body having aseparable portion at the distal end region adapted to allow passage of aguidewire within the lumen to be removed from the distal end regionthrough the separable portion, a first side opening in the tubular body,and a second side opening in the tubular body, the second side openingbeing located between the first side opening and the separable portionand adapted for threading the guidewire from the distal end into thelumen under the separable portion, out of the second side opening over aportion of the tubular body, into the first side opening and into thelumen through the proximal end.

Yet another aspect of the invention relates to a method for placing astent assembly in a bifurcated vessel using the aforementionedspecialized catheter, the method comprising: (a) locating and assessingan area in the body for placement of a stent assembly in a primaryvessel and a secondary vessel at a location where the primary vessel andthe secondary vessel intersect at a bifurcation area; (b) inserting aprimary guidewire from a location external of the body through theprimary vessel beyond the bifurcation area; (c) inserting a secondaryguidewire from a location external of the body through the primaryvessel and into the secondary vessel; (d) selecting a primary stenthaving a lumen, a first side opening, a proximal end region and a distalend region terminating at a distal end of the primary stent, the primarystent being configured to fit within the primary vessel in thebifurcation area, and when expanded, to maintain patency of the primaryvessel where the primary stent is installed; (e) mounting the primarystent on a primary stent catheter, the primary stent catheter having atubular body, a lumen extending through the tubular body, a proximal endof the tubular body, a distal end region terminating at a distal end ofthe tubular body opposite the proximal end, the tubular body having aseparable portion at the distal end region, a first side opening in thetubular body, and a second side opening in the tubular body, the secondside opening being located between the first side opening and theseparable portion, such that the primary stent is expandable when inposition in the bifurcation area and the first side opening of theprimary stent is aligned with the first side opening of the primarystent catheter; (f) inserting the primary guidewire from the distal endof the tubular body through the lumen of the primary stent cathetersurrounded by the distal end portion of the primary stent, extendingthrough the lumen of the primary stent catheter surrounded by theproximal end region of the primary stent, and through the proximal endof the tubular body; (g) inserting the secondary guidewire through thedistal end of the tubular body into the lumen under the separableportion, out of the second side opening of the primary stent catheter,over a portion of the tubular body, into the aligned first side openingsof the primary stent and primary stent catheter, extending through thelumen of the primary stent catheter surrounded by the proximal endregion of the primary stent, and through the proximal end of the tubularbody; (h) passing the primary stent catheter through the primary vesseland into the bifurcated area for placement of the primary stent withinthe primary vessel to a point such that the primary guidewire and thesecondary guidewire diverge and the secondary guidewire passes throughthe separable portion, thereby removing the secondary guidewire from thedistal end region; (i) expanding the primary stent to maintain patencyof the primary vessel in and adjacent to the bifurcation area, such thatthe first side opening in the primary stent is aligned with thesecondary vessel; (j) withdrawing the primary stent catheter and,optionally, the primary guidewire from the primary vessel, whileretaining the secondary guidewire in the primary and secondary vessels;(k) selecting a secondary stent having a lumen, a proximal end regionand a distal end region, the secondary stent being configured to fitwithin the secondary vessel in the bifurcation area, and when expanded,to maintain patency of the secondary vessel where the secondary stent isinstalled; (l) mounting the secondary stent on a secondary stentcatheter having a lumen such that the secondary stent is expandable whenin position through the first side opening of the primary stent in thebifurcation area and when in position in the secondary vessel; (m)inserting the secondary guidewire into the secondary stent catheterlumen beginning from a portion surrounded by the distal end region ofthe secondary stent and extending through the lumen of the secondarystent catheter surrounded by the proximal end region of the secondarystent; (n) passing the secondary stent catheter through the primaryvessel, through the proximal end region and first side opening of theexpanded primary stent into the bifurcated area for placement of thesecondary stent within the secondary vessel and in fluid communicationwith the expanded primary stent; (o) expanding the secondary stent tomaintain patency of the secondary vessel such that the proximal endregion of the secondary stent is in fluid communication and in contactwith the first side opening of the expanded primary stent; and (p)withdrawing the secondary stent catheter and the secondary guidewire,and the primary guidewire if the primary guidewire was not previouslywithdrawn, from the secondary and primary vessels to a location externalof the body.

Another aspect of the present invention relates to a balloon forexpanding a first balloon-expandable stent, the balloon comprising atubular balloon having a proximal end and a distal end, the balloonbeing capable of receiving within its tubular structure a guidewire fordeployment of the first stent, the balloon further comprising a sideopening closer to the distal end than the proximal end though which asecond guidewire and a second stent may pass.

As used herein, the article “a,” “an” or a singular component includesthe plural or more than one component, unless specifically andexplicitly restricted to the singular or a singular component. Thus, forexample, reference to “a secondary vessel” means one or more than onesecondary vessel that may be associated with a primary vessel as part ofa bifurcated vessel.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe invention, will be better understood when read in conjunction withthe appended drawings. For the purpose of illustrating the invention,there are shown in the drawings embodiments which are presentlypreferred. It should be understood, however, that the invention is notlimited to the precise arrangements and instrumentalities shown.

In the drawings:

FIG. 1 is a schematic representation of a bifurcated vessel showing theinsertion of primary and secondary guidewires therein as initial stepsin the method of the present invention prior to the placement of thestent assembly in the desired location within a bifurcated vessel.

FIG. 2 is a schematic representation of a first embodiment of a primarycatheter, sheath and stent assembly for inserting a self-expandingprimary stent within the primary vessel in accordance with oneembodiment of the method of the present invention.

FIG. 3 depicts schematically an enlarged end elevation view of theprimary catheter, sheath and stent assembly of FIG. 2 taken along lines3-3 of FIG. 2.

FIG. 4 schematically represents the alignment of the primary catheter,sheath and stent assembly of the first embodiment in the primary vesselsuch that the side openings in the primary stent catheter, the primarystent and the primary stent sheath are aligned with the opening to thesecondary vessel in the bifurcation area prior to expansion of theprimary stent in the primary vessel.

FIG. 5 schematically illustrates the placement of the primary stentwithin the primary vessel after the removal of the primary stentcatheter assembly, but with the preferred retention of the primaryguidewire, while retaining the secondary guidewire in place within thesecondary vessel.

FIG. 6 schematically illustrates the insertion of an unexpandedself-expandable secondary stent on a secondary stent catheter and sheathassembly prior to insertion of the secondary stent into the secondaryvessel.

FIG. 7 schematically illustrates the insertion of the unexpandedsecondary stent into the secondary vessel through the side opening inthe primary stent.

FIG. 8 schematically represents the placement of the expanded stentassembly within the bifurcated vessel after removal of the catheterassemblies and guidewires.

FIG. 9 is a schematic representation of an alternative embodiment of aprimary stent catheter assembly for insertion of a balloon-expandableprimary stent within the bifurcated vessel, prior to the expansion ofthe stent, using a first embodiment of a particularly constructedballoon for the method of inserting primary and secondary stents inbifurcated vessels in accordance with the present invention.

FIG. 10 depicts schematically an enlarged end elevation view of theprimary catheter, sheath and stent assembly of the alternativeembodiment of FIG. 9 taken along lines 10-10 of FIG. 9.

FIG. 11A is a schematic representation, in a side elevation view, ofanother alternative embodiment of a primary stent catheter assemblycomprising a primary stent catheter, self-expandable primary stent, andprimary stent sheath, for inserting the self-expandable primary stentwithin a primary vessel in accordance with another embodiment of themethod of the present invention.

FIG. 11B is a schematic representation, in a side elevation view, of yetanother alternative embodiment of a primary stent catheter assembly, forinserting the self-expandable primary stent within the primary vessel inaccordance with an embodiment of the method of the present invention,wherein the primary stent catheter includes a first longitudinal slot.

FIG. 12A is a schematic representation, in a top elevation view, of theembodiment of FIG. 11A of the primary stent catheter assembly whereinthe self-expandable primary stent is partially exposed by the primarystent sheath.

FIG. 12B is a schematic representation, in a top elevation view, of theembodiment of FIG. 11B of the primary stent catheter assembly whereinthe self-expandable primary stent is partially exposed by the primarystent sheath.

FIG. 13 is a schematic representation of an alternative embodiment of aprimary stent catheter assembly for insertion of a balloon-expandableprimary stent within the bifurcated vessel, prior to the expansion ofthe stent, using a second, alternative embodiment of a particularlyconstructed balloon as shown in FIG. 17 for the method of insertingprimary and secondary stents in bifurcated vessels in accordance withthe present invention.

FIGS. 14A and 14B depict schematically enlarged end elevation views ofthe primary stent catheter assembly of FIG. 11A taken along lines 14-14of FIG. 11A. FIG. 14B depicts a further enlarged view of the boxed areaof FIG. 13A.

FIGS. 15A and 15B depict schematically enlarged end elevation views ofthe alternative embodiment of FIG. 13 taken along lines 15-15 of FIG.13, depicting the distal end view of the alternative embodiment of aballoon as shown in FIG. 17. FIG. 15B depicts a further enlarged view ofthe boxed area of FIG. 15A.

FIG. 16A depicts a schematically enlarged end elevation view of theprimary stent catheter of FIGS. 11A and 13 taken along lines 16-16 ofFIGS. 11A and 13.

FIGS. 16B-16E are further enlarged end elevation views of the primarystent catheter of the boxed area of FIG. 16A, wherein FIGS. 16B through16E are schematic representations of alternative embodiments of aseparable portion of the primary stent catheter embodiments of FIGS. 11Aand 13.

FIG. 17 is a schematic representation depicting a distal portion of analternative embodiment of a balloon, in an plan view orientation rotatedlongitudinally 90° compared to the orientation of the balloon shown inFIG. 13, for use with a balloon-expandable primary stent in the methodof the present invention for inserting primary and secondary stents inbifurcated vessels, where FIG. 17 shows a side opening and an optionalextension of the side opening to the distal end of the balloon.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to various embodiments of catheters andmethods of using them for placing a stent assembly in a bifurcatedvessel in an animal body, preferably a human, where the vessels may beany type of bifurcated vessel as mentioned above, but particularlyvascular vessels. Coronary vessels such as the aorta and its branches,renal arteries, great arch vessels such as subclavian, carotid andbrachiocephalic vessels, are particularly preferred. Also, although theschematic depictions and descriptions herein relate to the insertion ofa secondary stent into a single secondary vessel branching from aprimary vessel, the same method may be applied to two or more branchesextending from a primary vessel.

As mentioned above, any type of stent may be used, including stents ofvarious geometry made of stainless steel, titanium, nitinol,nickel-chromium alloys, cellulose, and various synthetic polymericplastics. Moreover, the primary and secondary stents used in the presentmethod may be of any desired or appropriate dimension in view of thevessels in which they are to be inserted, but typically, withoutlimitation, a primary stent has an expanded length of about 10 mm toabout 40 mm, while a secondary stent typically, but without limitation,has an expanded length of about 5 mm to about 40 mm. The uses of thestents in particular vessels determine their diameter and length and theangle of the secondary stent with respect to the primary stent. Forexample without limitation, when the primary vessel is the aorta or agreat arch vessel, the stents may have an expanded diameter of about 20mm to about 50 mm. The branch vessels from the aorta are appropriatelysized, and stents used therein may have an expanded diameter typicallyof about 4 mm to about 10 mm, while stents used in the secondary vesselsfrom the great arch vessel typically may have an expanded diameter ofabout 8 mm to about 15 mm. Stents used in other coronary vesselstypically may have an expanded diameter of about 2 mm to about 6 mm.Stents used with renal vessels typically may have an expanded diameterof about 4 mm to about 10 mm. The branched secondary vessels mayintersect with a primary vessel at any angle. Such angle may vary,depending on the bifurcated vessels, such as at an angle of about 20° toabout 120°, with typical angles being about 30°, about 45° and about90°. Preferably, a number of stents and their associated catheters areprepared at different angles to be ready for insertion when appropriate.

Additionally, the primary or secondary stents may be drug eluting stentsmade of or coated with an antirestentotic or antithrombogenic material.Typically, but again without limitation, the antirestentotic material isan antimetabolite. Exemplary antirestentotic materials includepaclitaxol, seruliomous, everulimous, antisense ribonucleic acid ornitric oxide, for instance. Non-limiting examples of antithrombogenicmaterials include heparin, enoxaprin, low molecular weight heparin,antithrombin, tissue plasminogen activator, streptokinase, urokinase andvarious antithrombogenic polymers. The materials may be coated either onthe primary stent, the secondary stent, or both, and may be in the formof a polymer reservoir or matrix allowing for the gradual release of thematerial.

As also noted above, the stents used in the method of the presentinvention may be self-expandable or balloon-expandable. Although FIGS.1, 5, 8, and 16A-16E are generic to all types of stents, for thepurposes of clarity in illustrating and explaining this invention, FIGS.2-4, 6, 7, and 11A-13B, are directed to the use of self-expandablestents, while FIGS. 9, 10, 13, 15A, 15B and 17 schematically depict theuse of a balloon-expandable primary stent, where the principle wouldapply also to a balloon-expandable secondary stent, which is notillustrated specifically for the sake of clarity, but such stents arewell known to those skilled in the art, and could be readily adapted tothe present method without undue experimentation.

In addition to the description of the method illustrated in FIGS. 1through 10, a specialized catheter and the method of its use will bedescribed with respect to FIGS. 11A through 16. The specialized catheterdepicted in FIGS. 11A through 16 functions similarly to the primarycatheter in the stent assembly of FIGS. 1 through 10. For this reason,the last two digits of the identifying numerals of FIGS. 11A through 16correspond generally to the last two digits of the identifying numeralsin FIGS. 1 through 10.

With reference to the drawings, wherein like numerals indicate likeelements throughout the several views, there is shown in FIG. 8 a stentassembly 10 after insertion into a bifurcated vessel 12, which is alsoclearly shown in FIG. 1. The bifurcated vessel 12 includes a primaryvessel 14 and at least one branch or secondary vessel 16 extending atany appropriate angle, such as about 20° to about 120°, with respect tothe primary vessel 14. As noted above, for clarity and purposes ofillustration, only one branch or secondary vessel 16 is illustrated,although two or more such secondary vessels, at any angles, could alsobe involved in the stent placement method according to the presentinvention. The primary vessel 14 and the secondary vessel 16 meet in abifurcation area 18 best shown in FIGS. 1 and 8.

Again with reference to FIG. 8, and also with reference to FIGS. 2, 4,6, and 11A, 11B, 12A and 12B, the stent assembly 10 includes a primarystent 24, 124 for expansion and implantation within the primary vessel14, 114. The primary stent 24, 124 includes a primary stent lumen 25,125, a proximal end region 26, 126, a distal end region 28, 128, and adistal end 29, 129. The embodiment of the primary stent 24 illustratedin FIGS. 2 and 4 includes a distal end region 28 and a side opening 30between the proximal and distal end regions. The embodiment of theprimary stent 124 illustrated in FIGS. 11A, 11B, 12A and 12B includes afirst side opening 130 between the proximal end region 126 and thedistal end 129.

The stent assembly 10 also includes a secondary stent 32, which may beidentical in all embodiments of the present invention. As a result,FIGS. 11A through 16E do not show a separate secondary stent or asecondary catheter, since the secondary stent 32 and catheter may beused and placed within the secondary vessel 116 as described regardingthe placement of the secondary stent 32 in the secondary vessel 32 withrespect to the first embodiment regarding FIGS. 1-10. The secondarystent 32 has a lumen 33, a proximal end region 34, and a distal endregion 36. The secondary stent 32 is implanted within the secondaryvessel 16, 116 such that its lumen 33 is in fluid communication with thelumen 25, 125 of the primary stent 24, 124 through the side opening 30(or first side opening 130) of the primary stent 24, 124. Preferably, asshown in FIG. 8, the end of the secondary stent 32 in the proximal endregion 34 is in contact with the wall of the primary stent 24, 124surrounding the side opening 30 (or first side opening 130). The sideopening 30 (or first side opening 130) may be of any appropriate shapeto correspond with the angle of the secondary stent 32 and the secondarystent 32 would have the appropriate shape to mate with the side opening30 (or first side opening 130) in the primary stent 24, 124 tocompletely support the bifurcated vessels.

Although bifurcated stent assemblies are known in the art, the presentinvention relates to a more efficient and positive placement orinsertion method with better alignment than is believed possible withprior art stent insertion methods resulting in a bifurcated stentassembly. Problems associated with such prior art insertion methodsinclude the need to fish a secondary guidewire into the secondary lumenafter the primary stent has been expanded, special shapes or angledportions of secondary stents, such as a flared proximal end portion,insertion methods which rely on the use of two balloons to expand aprimary stent while aligning a primary stent opening with the lumen ofthe secondary vessel, and other problems, where insertion is difficultor uncertain and/or time-consuming. The more difficult and timeconsuming the procedure, the more the patient or other subject is atrisk during and after the procedure. The insertion method of the presentinvention overcomes or at least reduces such problems and concerns.

With reference to FIG. 1, after an initial step of locating andassessing an area in the body for placement of a stent assembly in aprimary vessel 14 and a secondary vessel 16 at a location where theprimary vessel and the secondary vessel intersect at a bifurcation area18, a primary guidewire 20 is inserted from a location external of thebody through the primary vessel 14 beyond the bifurcation area 18.Typically, for certain coronary vessel angioplasty procedures andassociated stent insertion procedures, insertion of the guidewires isthrough an incision in a femoral artery. A secondary guidewire 22 isalso inserted from a location external of the body through the primaryvessel 14 and into the secondary vessel 16. The insertion of thesecondary guidewire 22 at the initiation of the procedure is animportant aspect in assuring appropriate and accurate alignment of thesecondary stent in the secondary vessel.

The remainder of the insertion method and further description of thespecialized catheter will now be described with respect to an embodimentin which the stents are self-expandable stents inserted as schematicallydepicted in FIGS. 2-7, 11A, 12A, 14A, 14B and 16A-16E, resulting in theplacement of the stent assembly 10 as shown and previously describedwith respect to FIG. 8.

After insertion of the guidewires as shown in FIG. 1, an appropriateprimary stent 24, 124 is selected such that the primary stent sideopening 30 (or first side opening 130) is appropriate in size andlocation with respect to the size and shape of the secondary vessel 16,116 in the bifurcation area 18, 118 as determined by prior examinationusing various diagnostic or even exploratory surgical techniques. Thestents used in the present invention are radio opaque or preferably haveradio opaque or other suitable markings, such as marking 35, 135 atleast at the proximal end region 34, 134 of the secondary stent 32, andoptionally at the distal end region 36 (not shown) and, with respect tothe primary stent 24, 124, markings 31, 131 in areas surrounding theside opening 30, (or first side opening 130), and optionally at theproximal and distal end regions 26, 126 and 28, 128. The markings, suchas markings 31, 131 and 35 (although distal markings are not shown inthe embodiment of enlarged FIGS. 11A through 16E), allow for theefficient travel and/or location of the stents in the body, and thesecondary stent within the primary stent, so that they can be locatedand assessed by any suitable technique, such as fluoroscopy, plainradiography, arteriogram, virtual arteriogram, computerized tomography,magnetic resonance imaging, or any other appropriate technique. Theprimary stent 24, 124 is also configured to fit within the primaryvessel 14, 114 in the bifurcation area 18, 118 and, when expanded, tomaintain patency of the primary vessel 24, 124 where the primary stentis installed, as shown in FIG. 8.

The embodiment depicted in FIGS. 1 through 8 includes the primary stent24 mounted on a primary stent catheter 38 having a lumen 40 and also aside opening 42 of a shape, size and location corresponding to the sideopening 30 of the primary stent 24 so that the openings will be inalignment.

As best shown in FIGS. 2 and 3, it is preferred, but not required, touse an optional peel-away wire guide 44 through which the secondaryguidewire 22 is inserted, as explained below. The peel-away wire guide44 includes side walls 46 attached to the surface of the primarycatheter 38 at a location distal to the distal region 28 of the primarystent 24. The attachment may be by any sort of suitable nontoxicadhesive, melt bonding, fusion welding, etc. The peel-away wire guide 44also includes a releasable closure member 48 of a type typically used inZIP-LOK® reclosable plastic bags. Thus, for example, in this type of areleasable closure 48, a longitudinal male rib, with or without a smallhook-like edge, is retained by friction within a longitudinal femalegroove with or without an interfitting hook edge reception slot forreleasably retaining the peel-away releasable closure 48 in a closedcondition upon pressing the components together. The releasable closurecan be opened either by manually separating the releasable membercomponents by pulling them apart, or by any other sufficient force whichovercomes the friction created by the press fit arrangement of thereleasable closure. The movement of a guidewire in a directiontransverse to the longitudinal closure members is sufficient to causethe friction to be overcome to release the guidewire.

The embodiment depicted in FIGS. 11A through 16E includes the primarystent 124, mounted on a primary stent catheter 138 having a lumen 140, aseparable portion 174 at the distal end region 178, a first side opening142 of a shape, size and location corresponding to the first sideopening 130 of the primary stent 124 so that the openings will be inalignment, and a second side opening 180, which may be in the form of alongitudinal slot, located between the first side opening 142 and theseparable portion 174, the second side opening 180 defining the proximalend of the separable portion 174. The primary stent catheter 138 mayalso have a longitudinal slot 186, best seen in the alternativeembodiments of FIGS. 11B and 12B, formed in an extension distal to theseparable portion 174.

As best shown in FIGS. 14A and 16A through 16E, the separable portion174 of the primary stent catheter 138 is contiguous with thecircumference of the primary stent catheter 138. The preferredembodiment is depicted by FIG. 16D, in which the primary stent catheter138 is split into a longitudinal male member 195 abutting a longitudinalfemale member 196, creating a releasable closure 197. In thisembodiment, the releasable closure 197 is of a type typically used inZIP-LOK® reclosable plastic bags. Thus, for example, in the releasableclosure 197, the longitudinal male member 195 frictionally interlockswith the longitudinal female member 196 for releasably retaining thereleasable closure 197 in a closed condition upon pressing thecomponents together. The releasable closure 197 can be opened either bymanually separating the releasable member components by pulling themapart, or by any other sufficient force which overcomes the frictioncreated by the press fit arrangement of the releasable closure 197. Themovement of a guidewire in a direction transverse to the longitudinalclosure members is sufficient to cause the friction to be overcome torelease the guidewire.

Alternative embodiments of the separable portion are depicted in FIGS.16B, 16C, and 16E. FIG. 16B illustrates the primary stent catheter 138being split into a longitudinal first portion 188 abutting alongitudinal second portion 190, creating a longitudinal slit 192.Another embodiment is shown in FIG. 16C, wherein the first portion 188and second portion 190 abut each other in an overlapping longitudinalslit 194. Another type of releasable closure 200 is illustrated in FIG.16E, in which the first portion 188 and second portion 190 are replacedby a hook portion 198 and a hook reception slot 199, respectively, inwhich the hook portion 198 is retained by friction within theinterfitting hook reception slot 199.

Since the initial embodiment of the primary stent 24, 124 is aself-expandable stent, to prevent the stent from expanding away from thesurface of the catheter 38, 138, a primary stent sheath 50, 150, havinga distal end 53, 153 at the distal region 28, 128 of the primary stent24, 124, as well as an opposed proximal end (not labeled) surrounds theprimary stent 24, 124. The primary stent sheath 50, 150 also includes aside opening 52, 152 of the same size, shape and location as the sideopenings 30 and 42 (or first side openings 130 and 142) in the primarystent 24, 124 and the primary stent catheter 38, 138, respectively, allof such openings being in alignment.

The primary stent sheath 50, 150 also includes a longitudinal groove orslot 54, 154 in the surface of a portion of the primary stent sheath 50,150 between the edge of the side opening 32, 132 and the distal end 53,153 of the primary stent sheath. The groove 54, 154 is best seen inFIGS. 2, 3, 11A, 12A, 12B, 14A and 14B. The purpose of this groove 54,154 is to allow the secondary guidewire 22, 122 to pass through thegroove when the sheath 50, 150 is retracted to allow the self-expandablestent to expand.

In the embodiment illustrated in FIGS. 1 through 8, once the primarystent 24 is mounted on the primary stent catheter 38 and surrounded bythe primary stent sheath 50, the primary guidewire 20 is insertedthrough the lumen 40 of the catheter 38, such that the primary guidewire20 extends fully through the primary catheter, stent and sheathassembly. The secondary guidewire 22 is inserted at least into thealigned side openings 30, 42 and 52 of the primary stent 24, primarystent catheter 38 and primary stent sheath 50, respectively, and intothe lumen 40 through the proximal end of the primary catheter, stent andsheath assembly. If the optional peel-away wire guide 44 is used, thesecondary guidewire 22 is also threaded through it.

In the embodiment illustrated in FIGS. 11A through 16E, once the primarystent 124 is mounted on the primary stent catheter 138 and surrounded bythe primary stent sheath 172, the primary guidewire 120 is insertedthrough the lumen 140 of the catheter 138, such that the primaryguidewire 120 extends fully through the primary catheter, stent andsheath assembly. The secondary guidewire 122 is inserted through thedistal end 129 of the primary stent catheter 138, into the lumen 140under the separable portion 174 of the primary stent catheter 138, outof the second side opening 180 of the primary stent catheter 138, over aportion of the primary stent catheter 138, into the aligned first sideopenings 130 and 142 and the side opening 152 of the primary stent 124,primary stent catheter 138 and primary stent sheath 150, respectively,and extending through the lumen 140 through the proximal end of theprimary stent catheter assembly.

After the primary guidewire 20, 120 and the secondary guidewire 22, 122are inserted into the primary stent catheter 38, 138, the catheter andits associated primary stent 24, 124 and primary stent sheath 50, 150are passed through the primary vessel 14, 114 along the primaryguidewire 20, 120 and the secondary guidewire 22, 122 until the assemblyreaches the bifurcation area 18, 118.

In the embodiment illustrated in FIGS. 1 through 8, at the point wherethe guidewires 20 and 22 diverge, as the primary catheter assembly isadvanced along the primary guidewire 20 through the primary vessel 14,the secondary guidewire 22 will be released from the peel-away wireguide 44 if such guide is in use.

In the embodiment illustrated in FIGS. 11A through 16E, at the pointwhere the guidewires 120 and 122 diverge, as the primary catheterassembly is advanced along the primary guidewire 120 through the primaryvessel 114, the secondary guidewire 122 will be released from the lumen140 of the primary stent catheter 138 through the separable portion 174.

In steps common to both embodiments of the present invention, thecatheter assembly is then advanced to a location such that the sideopenings 30, 42 and 52 (or first side openings 130 and 144 and sideopening 152) align with the secondary vessel 16, 116 in the bifurcationarea 18, 118. At that time, the primary stent 24, 124 is inserted intoposition within the primary vessel 14, 114. Typically, this isaccomplished by using a relatively stiff primary stent deployment wire56, 156 located between the primary stent catheter 38, 138 and theprimary stent sheath 50, 150. The primary stent deployment wire 56, 156also has a distal primary stent deployment wire abutment member 58, 158which abuts the proximal end of the primary stent 24, 124 to retain itin proper axial or longitudinal position on the catheter 38, 138 whilewithdrawing the primary stent catheter sheath 50, 150 from its retentionposition. When the sheath 50, 150 is withdrawn, by which the primarystent 24, 124 is retained on the catheter, the stent 24, 124 expands andbears against the walls of the primary vessel 14, 114, thus maintainingtheir patency. As the primary stent sheath 50, 150 is withdrawn out ofthe body, or at least off of the stent 24, 124, the secondary guidewire22, 122 passes through the groove 54, 154 in the sheath 50, 150. Theposition of the primary catheter, stent and sheath immediately prior tothe expansion of the primary stent 24 is shown in FIG. 4. Uponretraction of the sheath and the expansion of the primary stent 24, 124,the primary stent catheter 38, 138, the primary stent sheath 50, 150 andthe primary guidewire 20, 120 all may be withdrawn from the primaryvessel 14, 114, but the withdrawal of the primary guidewire 20, 120 maybe, and preferably is deferred until the secondary guidewire 22, 122 iswithdrawn and removed from the body as shown in FIGS. 5, 6 and 7.However, it is important that the secondary guidewire 22, 122 remain inthe primary vessel 14, 114 and especially in the secondary vessel 16 asshown in FIG. 5.

Once the primary stent 24, 124 has been inserted in the primary vessel14, 114 in the vicinity of the bifurcation area 18, 118, it is time toinsert the secondary stent 32 into the secondary vessel 16, 116. This isaccomplished by selecting a secondary stent 32 which is configured tofit within the secondary vessel 16, 116 in the bifurcation area 18, 118and, when expanded, such secondary stent 32 maintains the patency of thesecondary vessel 16, 116 when the secondary stent is installed andexpanded. As best shown in FIG. 6, the secondary stent 32 is mounted ona secondary stent catheter 60 having a lumen 62. Since the embodimentshown in FIG. 6 is a secondary stent that is self-expandable, asecondary stent sheath 64 overlies the secondary stent 32 to keep itfrom expanding by itself.

The secondary guidewire 22, 122 is then inserted into the secondarystent catheter lumen 62 beginning from a portion surround by the distalend region 36 of the secondary stent 32 and extending through the lumen62 of the secondary stent catheter 60 through the portion surrounded bythe proximal end region 34 of the secondary stent 32. Thus, thesecondary stent catheter, stent and sheath assembly are threaded ontothe secondary guidewire 22, 122 and the assembly passes through theprimary vessel 14, 114 until it reaches the bifurcation area 18, 118.

Upon reaching the bifurcation area 18, 118, as best shown in FIG. 7, theassembly travels along the guidewire 22, 122 through the side opening 30(or first side opening 130) in the expanded primary stent 24, 124 andinto the secondary vessel 16, 116. When the secondary stent, catheterand sheath assembly reaches the desired location within the secondaryvessel 16, 116, the secondary stent 32 is deployed by allowing it toexpand. This is accomplished in a manner similar to that described abovewith respect to the self-expandable primary stent 24, 124. Thus, asecondary stent deployment wire 66 having a secondary stent deploymentwire abutment member 68 bears against the proximal end of the secondarystent 32, retaining it in the appropriate longitudinal position on thesecondary stent catheter 38 while the secondary stent sheath 64 iswithdrawn toward the body exterior, exposing the secondary stent 32 andallowing it to expand into the appropriate position as shown in FIG. 8.When properly inserted and expanded, the secondary stent 32 is in fluidcommunication with the expanded primary stent 24, 124, and preferably,the proximal end of the secondary stent 32 is in contact with the wallof the primary stent 24, 124 surrounding the side opening 30 (or firstside opening 130) as shown in FIG. 8.

The stent assembly 10 shown in its deployed, expanded position in FIG.8, may be deployed using balloon-expandable stents, as well as by usingself-expandable stents as described above. FIGS. 9, 13, 15A, and 15Bdepict a schematic representation of a primary balloon-expandable stentand catheter assembly with respect to the insertion of aballoon-expandable primary stent 24′, 124′, where the primed referencenumerals identify the same elements as identified by the unprimedreference numerals of the embodiment shown in FIGS. 1-8, 11A, 12A, and16A-16E as described above. The embodiments depicted in FIGS. 13, 15Aand 15B show an assembly using an alternative embodiment of a balloon asbest shown in FIG. 17, constructed for use in inserting a primary stent,124′ into the primary vessel 114, and a secondary stent (not shown butcorresponding generally to stent 32, other than beingballoon-expandable) into the secondary vessel 116, compared to a firstballoon embodiment shown in FIG. 9. The method of placing a stentassembly in a bifurcated vessel using balloon-expandable stents issubstantially the same as that described above with the followingexceptions.

After locating and assessing an area in the body for placement of astent assembly in a primary vessel 14, 114 and a secondary vessel 16,116 where the primary and secondary vessels intersect at a bifurcationarea 18, 118, the primary guidewire 20, 120 and the secondary guidewire22, 122 are inserted into the vessels as described above and shown inFIG. 1. Then the appropriate balloon-expandable primary stent 24′, 124′is selected and mounted on a balloon 70, 170, which in turn is mountedon the primary stent catheter 38′, 138′. The balloon 70, 170 has a sideopening 72, 172 closer to the distal portion 173 of the balloon than theproximal (not shown) portion or end of the balloon and that is at leastof the same size and shape and that is aligned with the side opening 30′(or first side opening 130′) in the primary stent 24′, 124′ and sideopening 42′ (or first side opening 142′) formed in the primary stentcatheter 38′, 138′. The secondary guidewire 22, 122 and the secondarystent 32 extend through the side opening 72, 172 of the balloon 70, 170.

As shown in the alternative embodiment of FIGS. 13, 15A, 15B and 17, theside opening 172 may extend to the distal end 175 of the balloon 170.The distal extension of the side opening 172 may be simply the lack ofballoon structure at a portion leading to the distal end 175 of theballoon 170 or the extension may be in the form of a space having asmaller transverse distance than the transverse distance of the sideopening and of a dimension though which the guidewire is capable ofpassing that appears as a groove or slot 155 extending from the distalend 173 of the balloon to the side opening 172, as best seen in FIGS.15A and 15B. The extension of the opening 72, 172 to the distal endallows the deployment of the primary stent 24′, 124′ without interferingwith the secondary guidewire 22, 122, and enhanced retraction of theballoon 170 following the expansion of the primary stent 24′, 124′. Byforming a space in the form of a groove or slot 155 extending from theside opening 172 to the distal end 175 of the balloon 170, there is moreballoon structure at the distal portion 173 that can be used to bearagainst and thereby expand the distal portion of the primary stent 124′when the balloon 170 is expanded. An optional sheath 50′ including agroove 54′, while not required where a balloon stent assembly is used,preferably is optionally used to protect the primary stent 24′ and isshown as partially retracted in FIG. 9.

In the embodiment depicted in FIGS. 1 through 10, after the primaryballoon stent and catheter assembly shown in FIG. 9 has been assembled,the primary guidewire 20 extends into the lumen 40′ of the primary stentcatheter 38′. The secondary guidewire 22 is inserted either directlyinto the lumen 40′ through the side openings 30′, 42′ and 72 or isthreaded through the optional peel-away wire guide 44′, before enteringthe lumen 40′ through the side openings. Where a sheath 50′ is used, thesecondary guidewire 22 is also inserted into the side opening (notshown) of the sheath, as described above with respect to the firstembodiment.

The primary balloon catheter assembly is then advanced along theguidewires 20 and 22 in the primary vessel 14 until the distal endreaches the bifurcation area 18. At that point, as described above withrespect to the transition from FIGS. 2 and 4, where the primaryguidewire 20 and the secondary guidewire 22 diverge, the secondaryguidewire 22 is released from the peel-away wire guide 44′ such that theside openings 30′, 42′ and 72 are in alignment with the secondary vessel16.

In the embodiment depicted in FIGS. 11A through 16E, after the primaryballoon stent and catheter assembly shown in FIG. 13 has been assembled,the primary guidewire 120 extends into the lumen 140′ of the primarystent catheter 138′. The secondary guidewire 122 is inserted directlyinto the lumen 140′ under the separable portion 174′, out of the secondside opening 180′ of the primary stent catheter 138′, over a portion ofthe primary stent catheter 138′, into the first side openings 130′, 142′and side opening 172 of the balloon 170, and through the lumen 140′.

The primary balloon catheter assembly is then advanced along theguidewires 120 and 122 in the primary vessel 114 until the distal endreaches the bifurcation area 118. At that point, as described above withrespect to the transition from FIGS. 2 and 4, where the primaryguidewire 120 and the secondary guidewire 122 diverge, the secondaryguidewire 122 is released from the separable portion 174′ such that thefirst side openings 130′, 142′ and side opening 172 are in alignmentwith the secondary vessel 116.

Common to both aspects of the invention, the primary balloon stent 24′,124′ is then deployed by expanding the stent with pressure from theexpanding balloon 70, 170 provided by an appropriate fluid, such assaline solution, such that the primary balloon stent 24′, 124′ wouldhave the position shown for the self-expandable stent 24, 124 depictedin FIG. 5, to maintain the patency of the primary vessel 14, 114.Thereafter, the primary stent catheter 38′, 138′, the balloon 70, 170may be withdrawn from the primary vessel 14, 114. While the primaryguidewire 20, 120 may also be withdrawn at this stage, it is preferredto leave the primary guidewire 20, 120 within the primary vessel 14,114, so as to leave the arrangement as shown in FIG. 5, where theprimary stent 24′, 124′ has been expanded and deployed, the primaryguidewire 20, 120 remains within the primary vessel 14, 114 and thesecondary guidewire 22, 122 remains in the primary vessel 14, 114 andextends into the secondary vessel 16, 116.

A secondary balloon stent (not shown) is then mounted around a secondaryballoon (not shown), which in turn is mounted on a secondary stentcatheter (not shown). All of these components, while not shown in thedrawings, are similar to the arrangement shown in FIG. 6 for theself-expandable catheter, stent and sheath assembly. Since a ballooncatheter is being used, a secondary sheath is not required, but is alsooptional. The secondary guidewire 22, 122 is then threaded into a lumenin the secondary catheter and the secondary catheter and secondary stentassembly are moved along the secondary guidewire through the sideopening 30 (or first side opening 130) in the expanded primary stent 24,124 or 24′, 124′ into the bifurcation area 18, 118 and also into thesecondary vessel 16, 116 for appropriate expansion as described abovewith respect to FIGS. 7 and 8, but using the balloon expansion techniquedescribed above with respect to FIGS. 9 and 13. The resulting expandedballoon secondary stent would then be installed in the secondary vessel16, 116 to maintain the patency of the secondary vessel 16, 116 incommunication with the primary stent as shown in FIG. 8.

The specialized stent catheter and the method of its use in the presentinvention for placing a stent assembly in a bifurcated vessel in ananimal body is efficient and elegant, allowing for positive placementwithout overcrowding stents and catheters with excess balloons, externalguides for the guidewire, and other components. By threading the primarystent assembly, including any catheter, balloon or sheath used therewithalong both guidewires, and allowing for the release of the secondaryguidewire 22, 122 from the distal end of the primary catheter and stentassembly through the separable portion 174 of the primary stent catheter138, efficient and appropriate placement of the primary stent in thebifurcation area 18, 118 is accomplished readily. By removing theprimary catheter assembly and any associated sheaths or balloons afterthe expansion of the primary stent, along with the removal of theprimary guidewire 20, 120, the primary vessel is relieved of thatapparatus. Yet by retaining the secondary guidewire 22, 122 in positionwithin the primary vessel 14, 114 and the secondary vessel 16, 116,easy, efficient and positive location and alignment of the secondarystent 32 within the secondary vessel 16, 116 is accomplished readily byadvancing the secondary stent and catheter assembly along the secondaryguidewire into position passed the bifurcation area 18, 118 and into thesecondary vessel 16, 116. This allows for the complete support of thebifurcated vessel 12, 112 by the primary stent 24, 124 and secondarystent 32, as shown in FIG. 8.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

1. A catheter system comprising a catheter having a tubular body, a lumen extending through the tubular body, a proximal end of the tubular body, a distal end region terminating at a distal end of the tubular body opposite the proximal end, the tubular body having a separable portion at the distal end region; a guidewire passing within the lumen and removable transversely from the distal end region of the catheter through the separable portion; the catheter having a first side opening in the tubular body and a second side opening in the tubular body, the second side opening being located between the first side opening and the separable portion; the guidewire being threaded from the distal end of the catheter into the lumen under the separable portion, out of the second side opening over a portion of the tubular body, into the first side opening and out of the lumen through the proximal end.
 2. The catheter system of claim 1, wherein the separable portion is longitudinally separable.
 3. The catheter system of claim 1, wherein the second side opening is aligned with the first side opening.
 4. The catheter system of claim 1, further comprising a first longitudinal slot which is distal to the separable portion and which extends to the distal end of the catheter.
 5. The catheter system of claim 4, wherein the second side opening is a second longitudinal slot aligned with the first longitudinal slot.
 6. The catheter system of claim 1, wherein the separable portion comprises a longitudinal slit in the tubular body.
 7. The catheter system of claim 1, wherein the separable portion comprises a longitudinal first portion overlapping with a longitudinal second portion.
 8. The catheter system of claim 1, wherein the separable portion comprises a longitudinal male member frictionally interlocking with a longitudinal female member.
 9. The catheter system of claim 8, wherein the longitudinal male member has a longitudinal hook portion that is frictionally retained within a longitudinal female groove having a hook edge reception slot for receiving the longitudinal hook portion.
 10. A method for placing a stent assembly in a bifurcated vessel in an animal body, the method comprising: (a) locating and assessing an area in the body for placement of a stent assembly in a primary vessel and a secondary vessel at a location where the primary vessel and the secondary vessel intersect at a bifurcation area; (b) inserting a primary guidewire from a location external of the body through the primary vessel beyond the bifurcation area; (c) inserting a secondary guidewire from a location external of the body through the primary vessel and into the secondary vessel; (d) selecting a primary stent having a lumen, a first side opening, a proximal end region and a distal end region terminating at a distal end of the primary stent, the primary stent being configured to fit within the primary vessel in the bifurcation area, and when expanded, to maintain patency of the primary vessel where the primary stent is installed; (e) mounting the primary stent on a primary stent catheter, the primary stent catheter having a tubular body, a lumen extending through the tubular body, a proximal end of the tubular body, a distal end region terminating at a distal end of the tubular body opposite the proximal end, the tubular body having a separable portion at the distal end region, a first side opening in the tubular body, and a second side opening in the tubular body, the second side opening being located between the first side opening and the separable portion, such that the primary stent is expandable when in position in the bifurcation area and the first side opening of the primary stent is aligned with the first side opening of the primary stent catheter; (f) inserting the primary guidewire from the distal end of the tubular body through the lumen of the primary stent catheter surrounded by the distal end portion of the primary stent, extending through the lumen of the primary stent catheter surrounded by the proximal end region of the primary stent, and through the proximal end of the tubular body; (g) inserting the secondary guidewire through the distal end of the tubular body into the lumen under the separable portion, out of the second side opening of the primary stent catheter, over a portion of the tubular body, into the aligned first side openings of the primary stent and primary stent catheter, extending through the lumen of the primary stent catheter surrounded by the proximal end region of the primary stent, and out of the primary catheter lumen through the proximal end of the tubular body; (h) passing the primary stent catheter through the primary vessel and into the bifurcated area for placement of the primary stent within the primary vessel, to a point such that the primary guidewire and the secondary guidewire diverge and the secondary guidewire passes transversely through the separable portion, thereby removing the secondary guidewire from the distal end region; (i) expanding the primary stent to maintain patency of the primary vessel in and adjacent to the bifurcation area, such that the first side opening in the primary stent is aligned with the secondary vessel; (j) withdrawing the primary stent catheter and, optionally, the primary guidewire from the primary vessel, while retaining the secondary guidewire in the primary and secondary vessels; (k) selecting a secondary stent having a lumen, a proximal end region and a distal end region, the secondary stent being configured to fit within the secondary vessel in the bifurcation area, and when expanded, to maintain patency of the secondary vessel where the secondary stent is installed; (l) mounting the secondary stent on a secondary stent catheter having a lumen such that the secondary stent is expandable when in position through the first side opening of the primary stent in the bifurcation area and when in position in the secondary vessel; (m) inserting the secondary guidewire into the secondary stent catheter lumen beginning from a portion surrounded by the distal end region of the secondary stent and extending through the lumen of the secondary stent catheter surrounded by the proximal end region of the secondary stent; (n) passing the secondary stent catheter through the primary vessel, through the proximal end region and first side opening of the expanded primary stent into the bifurcated area for placement of the secondary stent within the secondary vessel and in fluid communication with the expanded primary stent; (o) expanding the secondary stent to maintain patency of the secondary vessel such that the proximal end region of the secondary stent is in fluid communication and in contact with the first side opening of the expanded primary stent; and (p) withdrawing the secondary stent catheter and the secondary guidewire, and the primary guidewire if the primary guidewire was not previously withdrawn, from the secondary and primary vessels to a location external of the body.
 11. The method of claim 10, wherein the separable portion of the primary stent catheter is longitudinally separable.
 12. The method of claim 10, wherein the second side opening in the primary stent catheter is aligned with the first side openings of the primary stent and primary stent catheter.
 13. The method of claim 10, wherein the primary stent catheter further comprises a first longitudinal slot which is distal to the separable portion of the primary stent catheter and which extends to the distal end of the primary stent catheter.
 14. The method of claim 13, wherein the second side opening is a second longitudinal slot aligned with the first longitudinal slot.
 15. The method of claim 10, wherein the animal is a human.
 16. The method of claim 15, wherein the bifurcated vessel is a vascular vessel.
 17. The method of claim 16, wherein the vascular vessel is a coronary vessel.
 18. The method of claim 10, wherein the primary stent is self-expandable, and wherein (e) of the method further comprises mounting the primary stent on the primary stent catheter and surrounding the mounted primary stent with a primary stent sheath having a distal end, a primary stent sheath side opening aligned with the first side openings of the primary stent catheter and the primary stent, and a longitudinal groove extending between the primary stent sheath side opening and a distal end of the primary stent sheath, whereby when the distal end of the primary stent sheath reaches a point of divergence of the primary guidewire and the secondary guidewire as the primary stent catheter passes through the primary vessel, the secondary guidewire passes through the groove to the aligned first side openings in the primary stent catheter and primary stent and the side opening in the primary stent sheath, and wherein (i) further comprises withdrawing the primary stent sheath to allow the primary stent to expand when in position in the bifurcation area.
 19. The method of claim 18, wherein the secondary stent is self-expandable, and wherein (l) further comprises mounting the secondary stent on the secondary stent catheter and surrounding the mounted secondary stent with a secondary stent sheath, and wherein (o) further comprises withdrawing the secondary stent sheath to allow the secondary stent to expand when the secondary stent is in position within the secondary vessel.
 20. The method of claim 10, wherein the primary stent is a balloon-expandable stent, and wherein (e) further comprises mounting the primary stent around a primary balloon which in turn is mounted on the primary stent catheter, the primary balloon having a primary balloon first side opening in alignment with the primary stent catheter first side opening and the primary stent first side opening, and wherein (i) further comprises expanding the primary balloon to expand the primary stent.
 21. The method of claim 20, wherein the secondary stent is a balloon-expandable stent and wherein (l) further comprises mounting the secondary stent around a secondary balloon which in turn is mounted on the secondary stent catheter, and wherein (o) further comprises expanding the secondary balloon to expand the secondary stent.
 22. The method of claim 10, wherein the secondary stent is inserted through the side opening of the primary stent, such that the secondary stent forms an angle of about 20° to about 120° with respect to the primary stent.
 23. The method of claim 22, wherein the angle is about 30°.
 24. The method of claim 22, wherein the angle is about 45°.
 25. The method of claim 22, wherein the angle is about 90°.
 26. The method of claim 10, wherein the primary stent has an expanded diameter of about 2 mm to about 50 mm, and the secondary stent has an expanded diameter of about 2 mm to about 15 mm.
 27. The method of claim 26, wherein the primary stent has an expanded diameter of about 20 mm to about 50 mm, and the secondary stent has a diameter selected from the group consisting of about 2 mm to about 6 mm, about 4 mm to about 10 mm and about 8 mm to about 15 mm.
 28. The method of claim 10, wherein the primary stent has an expanded length of about 10 mm to about 40 mm.
 29. The method of claim 10, wherein the secondary stent has an expanded length of about 15 mm to about 40 mm. 